Multi-stage shock absorber

ABSTRACT

A jounce control damping system with an elongated housing containing a damping medium, a primary piston assembly, a moveable outer piston assembly, and a movable inner piston assembly disposed at least partially within the outer piston assembly. The primary piston assembly provides a first compression damping force. The inner piston engages the primary piston assembly and provides a second compression damping force when moved in a compression direction. After the inner piston assembly moves a given distance, the outer piston assembly is moved in the compressive direction and provides a third compression damping force.

FIELD OF THE INVENTION

The present invention pertains to improvements in shock absorbers, andmore particularly to shock absorbers having position-dependent dampingforce characteristics.

BACKGROUND

Shock absorbers are used in vehicles to assist the vehicle in adaptingto different driving conditions due to irregularities in the road, suchas bumps, potholes, and other road surface anomalies. Shock absorbersare also used to assist a vehicle in traveling over more extremeconditions such as off-road driving.

In conditions such as off-road driving, the irregularities can be severeand may cause a standard shock absorber to bottom out, i.e. abruptlyreaching their maximum compression, producing a jarring impact. In orderto overcome this deficiency shock absorbers with jounce control havebeen developed. A jounce control shock absorber provides an elevateddamping force when the shock approaches the bottoming out condition.However, known jounce control systems are limited in their effectivenessdue to the fact that such system only provide one stage of an elevateddamping force.

SUMMARY OF THE INVENTION

The invention is directed to a system that implements a novel andunobvious jounce control shock absorber in the form of a jounce controlshock absorber with multi-stage jounce control.

One aspect of the jounce control damping system of the present inventioncomprises an elongated housing containing a damping medium, a moveableouter piston assembly disposed within the housing and a movable innerpiston assembly disposed at least partially within the outer pistonassembly. The inner piston assembly being configured to engage a primarypiston assembly as said primary piston assembly is moved beyond a firstcompression movement distance causing the inner piston assembly to movein the compressive direction. The outer piston assembly being configuredto move in the compressive direction in response to the inner pistonassembly moving in the compressive direction beyond a second compressivemovement distance. The primary piston assembly provides a firstcompression damping force during the first compression movement distanceof the primary piston. The inner piston assembly provides a secondcompression damping force greater than the first damping force duringthe second compression movement distance of the inner piston assemblyand the outer piston assembly provides a third compression damping forcegreater than the second compression damping force during the thirdcompression movement distance.

In another aspect of the present invention, the inner piston assemblycomprises an element for engaging the primary piston assembly. Theelement can be at least one aperture that permits the damping medium toflow through the aperture during movement of the inner piston in acompressive direction. The at least one aperture can also be configuredto engage an at least one valve assembly of the primary piston assemblyfor regulating the flow of the damping medium through the at least oneaperture during movement of the inner piston assembly in the compressivedirection.

It is a further aspect of the present invention for the inner pistonassembly to be disposed within a recessed cavity of the outer pistonassembly. An inner restoration spring may also be disposed in the outerpiston assembly recessed cavity and configured to provide an expansiveforce on the inner piston assembly. An outer restoration spring may alsobe provided in the elongated housing to provide an expansive force onthe outer piston assembly.

It is yet another aspect of the present invention for the outer pistonassembly to be disposed and moveable within a second housing. The secondhousing may be formed integral with the elongated housing.

It is further an aspect of the present invention for the second housingto be disposed and moveable in a third housing such that the secondhousing is configured to serve as a piston. When the second housing actsas a piston it may provide a fourth compression damping force greaterthan the third compression damping force during a fourth compressionmovement distance of the piston rod. In such an embodiment the secondhousing may comprise at least one aperture that permits damping mediumto flow from the third housing.

It is still a further aspect of the present invention to providemultistage damping system with an elongated housing containing a dampingmedium, an axially moveable primary piston assembly arranged in thehousing comprising a primary piston and a valve assembly, and an axiallymoveable secondary piston assembly. The axially moveable secondarypiston may have an orifice disposed in a location to engage the valveassembly when the primary piston assembly is moved in a compressivedirection beyond a particular compressive movement distance. When thevalve assembly engages the orifice, it regulates the flow of dampingmedium to provide a greater compressive damping force when said primarypiston assembly and said secondary piston assembly are moved beyond theparticular compressive movement distance. The invention may include anaxially moveable tertiary piston assembly having a recessed cavityformed therein with the secondary piston assembly disposed therein.

It is yet another aspect of the present invention to provide amultistage damping system with an elongated housing containing a dampingmedium, an axially moveable primary piston assembly arranged in thehousing comprising a first piston and a first element of a valveassembly, and an axially moveable secondary piston assembly having asecond element of a valve assembly disposed in a location to engage thevalve assembly first element when the primary piston assembly is movedin a compressive direction beyond a particular compressive movementdistance. When the first and second valve assembly elements are engagedthey flow of the damping medium is regulated to provide a greatercompressive damping force when the primary piston assembly and thesecondary piston assembly are moved beyond said particular compressivemovement distance.

BRIEF DESCRIPTION OF THE DRAWING

A more complete understanding of the present disclosure may be realizedby reference to the accompanying drawing in which:

FIG. 1 is a cross-sectional view of an exemplary shock absorberconfigured in accordance with the present invention;

FIG. 2A is a cross-sectional view of the shock absorber of FIG. 1 in afirst stage of operation;

FIG. 2B is a cross-sectional view of the shock absorber of FIG. 1 in asecond stage of operation;

FIG. 2C is a cross-sectional view of the shock absorber of FIG. 1 in athird stage of operation;

FIG. 2D is a cross-sectional view of the shock absorber of FIG. 1 in afourth stage of operation.

FIG. 3 is chart illustrating the compression damping force versusdistance provided by the exemplary shock absorber of FIG. 1.

The illustrative embodiments are described more fully by the Figures anddetailed description. The inventions may, however, be embodied invarious forms and are not limited to specific embodiments described inthe Figures and detailed description.

DETAILED DESCRIPTION

The invention is directed to a shock absorber advantageously for usewith a vehicle suspension. The shock absorber increases the dampingforce when there is significant travel of the vehicle suspension. Inparticular, as the suspension reaches a bottoming out condition duringcompression, the damping force of the shock absorber increases. Thepresent invention provides unique and novel mechanisms for increasingthe damping force depending on the position of the shock absorber duringcompression so as to significantly reduce or avoid a bottoming outcondition. As discussed below, the shock absorber of the presentinvention sequentially increases the damping force using a multi-stagejounce control configuration.

For the purposes of promoting an understanding of the principles of theinvention, reference will now be made to the embodiment illustrated inthe drawings and specific language will be used to describe the same. Itwill nevertheless be understood that no limitation of the scope of theinvention is thereby intended. The following illustrates the principlesof the disclosure. It will thus be appreciated that those skilled in theart will be able to devise various arrangements which, although notexplicitly described or shown herein, embody the principles of thedisclosure and are included within its spirit and scope.

All examples and conditional language recited herein are principallyintended expressly to be only for pedagogical purposes to aid the readerin understanding the principles of the disclosure and the conceptscontributed by the inventor to furthering the art, and are to beconstrued as being without limitation to such specifically recitedexamples and conditions.

Moreover, all statements herein reciting principles, aspects, andembodiments of the disclosure, as well as specific examples thereof, areintended to encompass both structural and functional equivalentsthereof. Additionally, it .is intended that such equivalents includeboth currently known equivalents as well as equivalents developed in thefuture, i.e., any elements developed that perform the same function,regardless of structure.

FIG. 1 shows a cross-sectional perspective view of an exemplary shockabsorber 10 in accordance with the present invention. The shock absorber10 comprises an elongated housing 100 with a first piston 120 coupled topiston rod 110 forming a primary piston assembly. First piston 120 isslidably received within the inner diameter of elongated housing 100.First piston 120 separates the internal volume of housing 100 into aprimary compression volume 101 located between piston 120 and the distalend of the shock absorber and a rebound volume 102 located betweenpiston 120 and the proximal end of the shock absorber.

First piston 120 includes valves 121 and 122. Valve 121 permits thedamping medium to flow from the compression volume 101 to the reboundvolume 102. Valve 122 permits fluid to flow from the rebound volume 102to the compression volume 101. The distal end of first piston 120comprises a piston rod valve assembly 105 that engages second piston 130as the piston rod 110 moves in the compressive direction. The piston rodvalve assembly 105 controls the flow of the damping medium throughapertures in the second piston 130 and flask 140. For the reasonsdiscussed below, the flask 140 is alternatively referred to as thirdpiston 140.

Also disposed within housing 100 are a flask 140 and cup 150, whichhouse second 130 piston and third 140 piston, respectively. Disposedwithin flask 140 is second piston 130. Second piston 130 is slidablyreceived within the inner diameter of flask 140. Second piston 130 formsa second compression volume 131 between second piston 130 and the distalend of flask 140. Second piston 130 comprises at least one aperture 132through which the damping medium may flow as the second piston 130 movesin the compressive direction.

Also disposed within flask 140 is a first return spring 135. In thedepicted embodiment, first return spring 135 is a conical spring thatreduces to the thickness of the wire diameter upon compression. However,it should be understood by one having ordinary skill in the art, thatother types of springs are useable for first return spring 135including, for example, wave springs, Belleville springs, and the likethat are known in the art. The first return spring 135 provides anexpansive force on second piston 130 and returns the second piston 130to its initial position when the piston rod 110 moves in the expansivedirection.

Flask 140 is disposed at least partially in cup 150. Flask 140 isslidably received within the inner diameter of cup 150 and acts as athird piston. Flask 140 forms a third compression volume 151 betweenflask 140 and the distal end of cup 150. The distal end of flask 140comprises an aperture 141 through which the damping medium may flow asthe third piston 140 moves in the compressive direction. Cup 150 may beformed integral with the housing. Also disposed within cup 150 is asecond return spring 145.

In the depicted embodiment in FIG. 1, second return spring 145 is aconical spring that reduces to the thickness of the wire diameter uponcompression. As with the first return spring 135, alternative springtypes are useable for the second return spring 145. The second returnspring 145 provides an expansive force on flask 140 and returns thethird piston 140 to its initial position when the piston rod 110 movesin the expansive direction.

The shock absorber 10 also includes a second cylinder 200 incommunication with the main tube 100. The second cylinder 200 includes areserve piston 210 that separates gas reservoir 220 from damping mediumchamber 230. A flow path 240 permits the damping medium to flow betweenthe primary compression chamber and the damping medium chamber 230.

FIGS. 2A-2D provide a cross-sectional view of the shock absorber 10 ofFIG. 1 and illustrate the characteristics of the shock absorber during acompression cycle. FIG. 3 provides a chart illustrating the compressiondamping force versus distance provided by shock absorber 10 as the shockabsorber moves through the three compression stages discussed below.

As shown in FIG. 2A, initially, during a first compression stage ofshock absorber 10, piston rod 110 and first piston 120 are moved in thecompressive direction, i.e. the distal direction, over a first distanceand provide a first compression damping force 310 (shown in FIG. 3).During the first compression stage the valve 121 regulates flow of thedamping medium from the compression volume 101 to the rebound volume 102as depicted by flow arrows 300. This causes the size of the compressionvolume 101 to be reduced and the rebound volume 102 to enlarge. Thefirst compression stage continues until the piston rod valve assembly105 engages second piston 130.

As shown in FIG. 2B, when the first piston assembly compresses beyondthe first distance, the piston rod valve assembly 105 will engage secondpiston 130 and the assembly 105 covers the at least one aperture 132 ofsecond piston 130. The piston rod valve assembly 105 communicates withthe aperture 132 of second piston 130 and controls the flow of thedamping medium through the aperture 132 as depicted by flow arrows 301.After engagement, as the piston rod 110 begins to move in thecompressive direction over a second distance, a second compression stagebegins. During the second compression stage, the combination of thepiston rod valve assembly 105 with the second piston 130 provides asecond compression damping force 320 that is greater than the firstcompression damping force 310 (shown in FIG. 3).

During the second compression stage the piston rod valve assembly 105permits the damping medium to flow from the second compression volume131 to the primary compression volume 101. This causes the size of thesecond compression volume 131 to be reduced. The second compressionstage continues until the second piston rod reaches the distal end offlask 140.

When the second piston 130 reaches the distal end of flask 140, flask140 acting as the third piston begins to move in the compressivedirection over a third distance. This provides the beginning of a thirdcompression stage. During the third compression stage, the piston rodvalve assembly 105 controls the flow of the damping medium from thethird compression volume 151 through the aperture 141 at the distal endof flask 140. This causes the size of the third compression volume 151to be reduced. The combination of the piston rod valve assembly with theflask 140 provides a third compression damping force 330 that is greaterthat the first compression damping force 310 and second compressiondamping force 320 (shown in FIG. 3).

It should be readily understood that selection of the dimensions for thehousing and valves configurations enable a shock designer to change thecorresponding damping forces provided. The damping forces useable for aparticular automotive or other application are determined based upon,for example, the weight of the vehicle, type of suspension and intendedapplication. Exemplary ranges for damping forces for first, second andthird compression damping forces include, for example, 0.6 kN-2.0 kN,4.0 kN-8.0 kN, and 8.0 kN-12.0 kN, respectively.

Likewise, exemplary ranges for the first, second and third compressiondistances from full compression include for example, 150 mm-300 mm, 35mm-70 mm and 0 mm-35 mm, respectively. The damping force for eachcompression stage is chosen by optimizing or altering the components ofthe shock absorber described herein. For instance, the damping force canbe controlled by the valve disc selection in pistons 120 and 105. Also,the damping force in the third zone can be controlled by modifying theinternal diameters of the flask 140 and cup 150. The engagement point ofthe second piston 130 to piston rod valve assembly 105 or the engagementpoint of the second piston 130 to the distal end of flask 140 can beused to alter damping force timing.

While the invention has been described in based on the above example,those skilled in the art will recognize that the invention is notlimited to this particular embodiment. The above description points outthe fundamental novel features of the invention as applied to apreferred embodiment. It will be readily recognized by those skilled inthe art that various omissions and substitutions and changes in the formand details of the devices illustrated, and in their operation, may bemade without departing from the spirit of the invention.

For example, it is expressly intended that all combinations of thoseelements which perform substantially the same function in substantiallythe same way to achieve the same results are within the scope of theinvention. Moreover, it should be recognized that structures and/orelements shown and/or described in connection with any disclosed form orembodiment of the invention may be incorporated in any other disclosedor described or suggested form or embodiment as a general matter ofdesign choice. It is the intention, therefore, to be limited only asindicated by the scope of the claims appended hereto.

Further, while the example shown above employed a single aperture 132,141 in the second piston 130 and third piston 140, it should be readilyapparent to one skilled in the art, that a shock absorber in accordancewith the invention may alternatively employ, for example, second 130 andthird 140 pistons with multiple apertures that permit the damping mediumto flow out of a compression volume.

Still further, one skilled in the art may alternatively dispose thepiston rod valve assembly 105 on the second piston 130 instead of thedepicted location on the piston rod 110 in FIGS. 1 and 2A-2D. In such anembodiment, valve assembly 105 would be coupled or integral with secondpiston 130. Either piston rod 110, first piston 120, or another elementcoupled to either element would contact the valve assembly 105 andconsequently move second piston 130 in the compressive direction with adesired damping force.

We claim:
 1. A jounce control damping system comprising: an elongatedhousing containing a damping medium; a moveable outer piston assemblydisposed within the housing; a movable inner piston assembly disposed atleast partially within the outer piston assembly; said inner pistonassembly being configured to engage a primary piston assembly as saidprimary piston assembly is moved beyond a first compression movementdistance causing the inner piston assembly to move in the compressivedirection; and said outer piston assembly being configured to move inthe compressive direction in response to the inner piston assemblymoving in the compressive direction beyond a second compressive movementdistance, wherein the primary piston assembly provides a firstcompression damping force during the first compression movement distanceof the primary piston; wherein the inner piston assembly provides asecond compression damping force during the second compression movementdistance of the inner piston assembly and the outer piston assemblyprovides a third compression damping force greater than the secondcompression damping force during the third compression movementdistance.
 2. The system of claim 1, wherein the inner piston assemblycomprises an element for engaging the primary piston assembly.
 3. Thesystem of claim 2, wherein said element comprises at least one aperturethat permits the damping medium to flow through the aperture duringmovement of the inner piston in a compressive direction.
 4. The systemof claim 3, wherein the at least one aperture is configured to engage anat least one valve assembly of the primary piston assembly forregulating the flow of the damping medium through the at least oneaperture during movement of the inner piston assembly in the compressivedirection.
 5. The system of claim 1, wherein said inner piston assemblyis disposed within a recessed cavity of the outer piston assembly. 6.The system of claim 5, further comprising an inner restoration springdisposed in the outer piston assembly recessed cavity and configured toprovide an expansive force on the inner piston assembly.
 7. The systemof claim 1 further comprising a second housing wherein the outer pistonassembly is disposed and moveable within the second housing.
 8. Thesystem of claim 7 wherein the second housing is formed integral with theelongated housing.
 9. The system of claim 1, wherein at least a portionof the second housing is disposed and moveable in a third housing suchthat the second housing is configured to serve as a piston.
 10. Thesystem of claim 9, wherein the second housing when operating as a pistonprovides a fourth compression damping force greater than the thirdcompression damping force during a fourth compression movement distanceof the piston rod.
 11. The system of claim 10, wherein the secondhousing comprises at least one aperture that permits damping medium toflow from the third housing.
 12. The system of claim 1, furthercomprising an outer restoration spring in said elongated housing forproviding an expansive force on the outer piston assembly.
 13. Amultistage damping system comprising: an elongated housing containing adamping medium; an axially moveable primary piston assembly arranged inthe housing comprising a primary piston and a valve assembly; and anaxially moveable secondary piston assembly having an orifice disposed ina location to engage said valve assembly when said primary pistonassembly is moved in a compressive direction beyond a particularcompressive movement distance, wherein said valve assembly once engagedwith said orifice regulates the flow of damping medium to provide agreater compressive damping force when said primary piston assembly andsaid secondary piston assembly are moved beyond said particularcompressive movement distance.
 14. The system of claim 13 furthercomprising an axially moveable tertiary piston assembly having arecessed cavity formed therein, wherein said secondary piston assemblyis disposed within said recessed cavity.
 15. The system of claim 14further comprising a first restoration spring disposed in the recessedcavity and configured to provide providing an expansive force on thesecondary piston assembly.
 16. The system of claim 1 further comprisinga second housing wherein the tertiary piston assembly is disposed andmoveable within the second housing.
 17. The system of claim 16 whereinthe second housing is formed integral with the elongated housing. 18.The system of claim 16, wherein the tertiary piston assembly isconfigured to provides a third compression damping force greater thanthe second compression damping force during a third compression movementdistance of the piston assemblies.
 19. The system of claim 16, whereinthe tertiary piston assembly comprises at least one aperture configuredto permits the damping medium to flow into said secondary pistonassembly.
 20. The system of claim 16 further comprising a secondrestoration spring configured to provide an expansive force on thetertiary piston assembly.
 21. A multistage damping system comprising: anelongated housing containing a damping medium; an axially moveableprimary piston assembly arranged in the housing comprising a firstpiston and a first element of a valve assembly; and an axially moveablesecondary piston assembly having a second element of a valve assemblydisposed in a location to engage said valve assembly first element whensaid primary piston assembly is moved in a compressive direction beyonda particular compressive movement distance, wherein said first andsecond valve assembly elements once engaged with one another regulatethe flow of damping medium to provide a greater compressive dampingforce when said primary piston assembly and said secondary pistonassembly are moved beyond said particular compressive movement distance.22. The system of claim 21, wherein said second element of said valveassembly is an orifice.